The influence of botulinum toxin (BTX) on chemical coding of nerve
fibers supplying canine urinary bladder
Article published in Urologia Polska 2008/61/Supl. 1.
Sylwia Lew, Agnieszka Bossowska, Joanna Wojtkiewicz, Andrzej Borkowski, Piotr Radziszewski, Zygmunt Kuleta, Mariusz Majewski
- Zespół Chorób Wewnętrznych, Wydział Medycyny Weterynaryjnej, Uniwersytet Warmińsko-Mazurski w Olsztynie
Katedra Fizjologii Człowieka, Wydział Nauk Medycznych, Uniwersytet Warmińsko-Mazurski w Olsztynie
Klinika Urologii Ogólnej, Onkologicznej i Czynnościowej Warszawskiego Uniwersytetu Medycznego
Introduction. Botulinum toxin is a selective blocking agent of acetylcholine release from nerve terminals what leads to the cessation of neural transmission. Injection of BTX into the urinary bladder wall causes a chemical denervation, where the toxin destroys not only the motor endplate, but also the whole axon. As of now, there is no data concerning the influence of BTX on the innervation pattern of the urinary bladder in the dog, a species that may be used as a model for studying some of the illnesses of human lower urinary tract.
Objectives. This study aimed at revealing the distribution and chemical coding patterns of nerve fibers supplying the urinary bladder of dogs, a week before and a week after the injection of BTX into the bladder wall, in order to broaden our knowledge concerning the mechanism(s) of botulinum toxin action.
Materials and methods. This study was conducted on 6 clinically healthy bitches of mixed breeds. Pieces of the whole thickness of urinary bladder wall were collected for immunohistochemical examination one week before the BTX was injected into the organ, as well as one week after the application of the drug into the organ wall. Chemical coding of nerve fibers was examined on 10-μm-thick frozen sections by means of a routine immunofluorescence technique using primary antibodies against Leu5- enkephaline (LENK), neuropeptide Y (NPY), calcitonine gene-related peptide (CGRP), vesicular acetylcholine transporter (VAChT), vasoactive intestinal peptide (VIP), nitric oxide synthase (NOS), galanine (GAL), substance P (SP), pituitary adenylate cyclase-activating peptide (PACAP), dopamine β-hydroxylase (DβH), and tyrosine hydroxylase (TH). Antigen-antibody complexes were visualized by using secondary antibodies marked with FITC or CY-3.
Results. All of the examined substances were found in the nerves supplying the muscular coat of the urinary bladder. The most numerous subset was formed by meshlike arranged VAChT-immunoreactive (VAChT-IR) terminals, while the NPY- or VIP-IR nerves were found to be moderate in number, and the CGRP- or LENK-IR ones were less numerous than the NPY- or VIP-IR terminals. Nerves containing NOS or GAL were sporadically observed. In the submucosal layer, NPY-IR nerves were moderate in number, while the LENK-, CGRP- VAChT- or VIP-IR processes were sporadically seen. A few nerve fibers found under the urothelium belonged exclusively to the NPY- or VIP-IR
- subpopulations. Injections of BTX caused a dramatic remodeling of the innervation pattern of the canine urinary bladder: while BTX lead to a distinct decrease in the number of nerve fibers containing VAChT, CGRP or VIP, a simultaneous increase in the number of nerve terminals containing NPY or NOS was also found.
Conclusions. Thus, as may be judged from the present results, the application of BTX into the wall of the canine urinary bladder lead, just after one week after the BTX injections, to a distinct remodeling of its innervation pattern, showing simultaneously that the toxin is able to influence both the sensory and parasympathetic components of the nerve system, and that the degenerative changes are simultaneously accompanied by restorative processes (also the inflammation-driven ones, as may be judged from the increase in the number of the NPY- or NOS-IR nerve terminals). However, the exact mechanism of BTX action in this species needs to be further